I bought a few PFC8574 and 4x4 keypads for a small project. I'm unclear on the correct wiring of the keypad to the PFC8574.
On the Arduino Playground's site, there are pull-up resistors for each column, but on a few other sites (like this one that I can't read, but I understand a schematic and there's a third example too, but I don't have the reputation to post it), the wiring does straight into the IC.
Does it depend on the library that's being used? Or what am I missing?